With increasing data rate demands among users, there is a substantial increase in demand for the licensed spectrum. However, the cellular licensed spectrum is already congested. Therefore to accommodate more number of users and improve the spectral efficiency, different methods such as cell sectoring, cell splitting, small cell deployment, relaying, etc. have been proposed in the past. However, these methods are still fall short of the desired data rate. Since the licensed band is unable to bring any more addition in data rate, the focus is being shifted to the use of unlicensed band of over 500 MHz around 5 GHz which is either unused or sparsely used.
In this direction, Licensed Assisted Access (LAA) under Long Term Evolution (LTE) uses unlicensed band at 5 GHz in addition to the licensed band allocated to LTE. Since it is an unlicensed band and every user is free to use this band, collision between transmissions can occur which reduces the effective data rate. Since WiFi and other similar technologies back-off from transmission if they sense the channel as busy, LAA should also refrain from transmission in case of contention or collision. Moreover as LAA uses a centralized scheduled Medium Access Control (MAC) protocol in comparison to the distributed MAC protocols of WiFi and other LAA should not completely grab the channel and starve WiFi or any other users.
In view of the above it becomes clear that while the use of unlicensed band is unavoidable, it becomes of paramount importance that fair co-existence of LAA and WiFi in unlicensed band